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<title>x86 Variable Attributes (Using the GNU Compiler Collection (GCC))</title>

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<h4 class="subsection" id="x86-Variable-Attributes-1"><span>6.34.15 x86 Variable Attributes<a class="copiable-link" href="#x86-Variable-Attributes-1"> &para;</a></span></h4>

<p>Two attributes are currently defined for x86 configurations:
<code class="code">ms_struct</code> and <code class="code">gcc_struct</code>.
</p>
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<dt><a class="index-entry-id" id="index-gcc_005fstruct-variable-attribute_002c-x86"></a>
<a id="index-ms_005fstruct-variable-attribute_002c-x86"></a><span><code class="code">ms_struct</code><a class="copiable-link" href="#index-ms_005fstruct-variable-attribute_002c-x86"> &para;</a></span></dt>
<dt><code class="code">gcc_struct</code></dt>
<dd>
<p>If <code class="code">packed</code> is used on a structure, or if bit-fields are used,
it may be that the Microsoft ABI lays out the structure differently
than the way GCC normally does.  Particularly when moving packed
data between functions compiled with GCC and the native Microsoft compiler
(either via function call or as data in a file), it may be necessary to access
either format.
</p>
<p>The <code class="code">ms_struct</code> and <code class="code">gcc_struct</code> attributes correspond
to the <samp class="option">-mms-bitfields</samp> and <samp class="option">-mno-ms-bitfields</samp>
command-line options, respectively;
see <a class="ref" href="x86-Options.html">x86 Options</a>, for details of how structure layout is affected.
See <a class="xref" href="x86-Type-Attributes.html">x86 Type Attributes</a>, for information about the corresponding
attributes on types.
</p>
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